Most religions predict such a day. Conspiracy theorists suggest that many world leaders have apocalyptic beliefs, and may even be attempting to cause Biblical prophecy to be fulfilled in 2012 via their actions. If it helps, the Bible says “But of that day and hour knoweth no one, not even the angels of heaven, neither the Son, but the Father only.”

But then again, maybe God changed his mind since the Bible was written, and told some people the date of the apocalypse? Maybe he told the ancient Mayans? Possibilities could be argued ad infinitum